1. Field of the Invention
The present invention relates to electronic units, electronically controlled mechanical timepieces, control programs for electronic units, recording media recording the programs, control methods for electronic units, and methods of manufacture for electronic units, and more particularly, to an electronic unit including a mechanical energy source, a generator driven by the mechanical energy source to generate induction electric power to supply electrical energy, and a rotation control unit driven by the electrical energy to control the rotation period of the generator.
2. Description of the Related Art
Japanese Examined Patent Publication No. Hei-7-119812 describes an electronically controlled mechanical timepiece in which mechanical energy obtained when a coil spring is released is converted to electrical energy by a generator, a rotation control unit is operated by the electrical energy to control current flowing through a coil of the generator, and hands fixed to a gear train are correctly driven to indicate the correct time.
In such an electronically controlled mechanical timepiece, a reference signal generated according to a signal sent from a time reference source such as a crystal oscillator is compared with a rotation detection signal corresponding to the rotation period of the generator to set the amount (for example, a period in which a brake is applied) of brake to be applied to the generator to adjust the speed of the generator.
In other words, when the rotation period of the generator becomes shorter than the period of the reference signal, the speed of the generator is adjusted such that a brake is applied for a longer period determined according to the phase difference thereof to make the rotation period of the generator longer to match the reference period.
When the rotation period of the generator rapidly becomes short due to a disturbance or for some other reason, however, brake control applies a brake for a long period in order to eliminate an indication error, so that the rotation period of the generator is made extremely long, which in effect stops the generator.
Therefore, although the rotation period temporarily becomes short due to a disturbance or for some reason, since a large amount of brake (long brake period) is applied according to the speed, the generator may be made to stop.
Once the generator stops, it is necessary to apply a very large torque to restart the generator due to the effect of cogging torque. Therefore, unless the coil spring is fully wound or nearly fully wound, the generator remains stopped and a duration time become short.
Even when the coil spring is fully wound and therefore the generator can be restarted, since it takes some time until the generator starts rotating, hands operating together with the rotation of the generator have an indication error.
A difficulty in which the generator is stopped due to such brake control may occur not only in electronically controlled mechanical timepieces but also in cases in which each operating section, such as a drum in a music box or a pendulum in a metronome, is operated at a high precision by precise brake control in various electronic units, such as music boxes, metronomes, toys, and electric shavers, having portions in which rotation is controlled by a mechanical energy source, such as a coil spring or a rubber band.
An object of the present invention is to provide an electronic unit, an electronically controlled mechanical timepiece, a control method for an electronic unit, and a method of manufacture for an electronic unit which prevent brake control from causing a generator to stop.
In one aspect of the present invention, an electronic unit including a mechanical energy source, a generator driven by the mechanical energy source to generate induction electric power to supply electrical energy, and a rotation control unit driven by the electrical energy to control the rotation period of the generator, the rotation control unit comprises: a brake control unit that compares a reference signal, generated according to a signal sent from a time reference source, with a rotation detection signal corresponding to the rotation period of the generator to apply brake control to the generator; and a generator-stop preventing unit that sets the amount of brake applied to the generator to a first brake setting value when a measured rotation period of the generator is equal to or longer than a first setting period, which is longer than a reference period, to prevent the generator from stopping.
In this case, it is preferred that the first brake setting value be set to a value which makes the amount of brake zero or the first brake setting value be set to a value equal to or less than the minimum amount of brake among a plurality of amounts of brake which can be set by the brake control unit.
In the present invention, when the rotation period of the generator becomes long and reaches the first setting period or longer, the amount of brake is set to the first brake setting value to control the generator. Since the first brake setting value is, for example, an amount of brake as small as zero or the minimum amount of brake or less, if control is made with the first brake setting value, unless the coil spring is unwound, the generator is prevented from being stopped.
It is also preferred that the generator-stop preventing unit sets the amount of brake applied to the generator to the first brake setting value in synchronization with the rotation period of the generator.
In such a structure, since the amount of brake can be immediately set to the first brake setting value if a rotation period equal to or longer than the first setting period is detected, quick control can be made.
It is further preferred that a period at which the generator is stopped, unless the amount of brake applied to the generator is switched to the first brake setting value, be selected as an upper limit, a period at which the generator vibrates when the amount of brake applied to the generator is switched to the first brake setting value be selected as a lower limit, and the first setting period be set to a period between the upper limit and the lower limit.
xe2x80x9cThe generator vibratesxe2x80x9d is a state in which a brake is applied for one reference period or more and a state in which a brake is not applied for one reference period are alternately repeated. In other words, it means that a fluctuation range of the actual rotation period of the generator against the reference period of the generator is large. When the reference period is 1/(8 Hz), for example, a wide range means a range of about 1/(10 Hz) to 1/(6 Hz), namely, a fluctuation range of, for example, 20% or more against the reference period. Therefore, a state in which the generator does not vibrate is a state in which some amount of brake is applied in one period, and the fluctuation range of the rotation period of the generator falls in a predetermined zone (such as, less than 15% of the reference period, or 1/((8xc2x11) Hz)).
When the first setting period, in which the amount of brake is set to the first brake setting value, which indicates a small brake power, is made short (close to the reference period), since a brake becomes ineffective or very small before the brake power is sufficiently applied, the generator is likely to vibrate.
On the other hand, when the first setting period is made long (very much larger than the reference period), the generator may be stopped before the amount of brake is changed to the first brake setting value.
Therefore, when the first setting period is set to a period which causes the generator neither to vibrate nor to stop, according to an electronic unit to which the present invention is applied, control is positively achieved so that a vibration state or a stop state of the generator does not occur.
The present invention is also preferably applied to an electronically controlled mechanical timepiece with a time indication unit operated with the rotation of the generator. The time indication unit indicates the time with hands, for example, coupled with an energy transfer unit, such as a gear train that transfers mechanical energy from a mechanical energy source to the generator.
According to an electronically controlled mechanical timepiece of the present invention, since the generator is prevented from being stopped, the duration is long, and re-activation of the generator after it is stopped can be prevented. Therefore, an indication error of the time indication unit (hands) is eliminated.
It is preferred that the electronic unit be a time measuring unit, a music box, or a metronome. A condition that the generator is stopped due to disturbance does not occur, and a time measuring unit, a music box, or a metronome in which rotation control is correctly performed can be provided.
The present invention also includes a control program, a recording medium recording the control program and a control method for an electronic unit comprising a mechanical energy source, a generator driven by the mechanical energy source to generate induction electric power to supply electrical energy, and a rotation control unit driven by the electrical energy to control the rotation period of the generator, in which the rotation control unit: compares a reference signal, generated according to a signal sent from a time reference source, with a rotation detection signal corresponding to the rotation period of the generator to apply brake control to the generator; and sets the amount of brake applied to the generator to a first brake setting value when a measured rotation period of the generator is equal to or longer than a first setting period, which is longer than a reference period, to prevent the generator from stopping.
When a control program according to the present invention, provided by a recording medium or through a communication channel, such as the Internet, is installed into an electronic unit, if the rotation period of the generator becomes long and reaches the first setting period or longer, since brake control is performed with the amount of brake used at the first brake setting value, the generator is positively prevented from being stopped. Therefore, correct rotation control is always performed in an operation state.
In addition, since this program can be installed into an electronic unit by a recording medium, such as a CD-ROM, or through a communication channel, such as the Internet, the first setting period can be most appropriately and easily set according to the characteristic of the electronic unit. Correct rotation control is thereby performed.
The present invention also includes a method of manufacturing an electronic unit comprising a mechanical energy source, a generator driven by the mechanical energy source to generate induction electric power to supply electrical energy, and a rotation control unit driven by the electrical energy to control the rotation period of the generator, the method comprising: selecting as an upper limit a period at which the generator is stopped unless the amount of brake applied to the generator is switched to a first brake setting value, selecting as a lower limit a period at which the generator vibrates when the amount of brake applied to the generator is switched to the first brake setting value, and setting a first setting period to a period between the upper limit and the lower limit, such that the electronic unit operates to: compare a reference signal, generated according to a signal sent from a time reference source, with a rotation detection signal corresponding to the rotation period of the generator to apply brake control to the generator; and set the amount of brake applied to the generator to a first brake setting value when a measured rotation period of the generator is equal to or longer than a first setting period, which is longer than a reference period, to prevent the generator from stopping.
When the first setting period, which serves as a reference for setting the amount of brake to the first brake setting value, which indicates a small amount of brake, is set to an inappropriate value, vibration occurs or the generator is stopped.
A period at which the generator vibrates or stops is changed according to the type of an electronic unit and a brake-force setting. According to a method manufacturing of the present invention, since each period is appropriately selected, the first setting period can be appropriately set so that the generator does not vibrate or the generator does not stop.